1. Field of the Invention
The invention relates to a hand free telephone system, and in particular relates to a telephone system with an ordinary analog telephone and a full-duplex speakerphone adapter.
2. Description of the Related Art
Hands-free speakerphone usages have become a common and important part of business conferences and daily telecommunications. Demand for good voice quality to facilitate efficient communications have increased, and the full-duplex feature for hands-free speakerphones has become highly desirable for business and home communications.
Conventionally, the most common speakerphones offer the ability to converse either in a handset mode or hands-free mode. FIG. 1A shows a conventional speakerphone 100 with a handset 72, a microphone 50 and a loudspeaker 51. A switch 191 on the speakerphone 100 determines whether the speakerphone 100 operates in the handset mode or hands-free mode. In the hands-free mode, users can be at a distance away from the speakerphone 100. The loudspeaker 51 conducts a telephone conversation without users holding the handset 72. Hands-free mode allows multiple participants to join the conversation in an audio-conference meeting, and also allows users to free up their hands for operating computer keyboards or other activities. FIG. 1B shows a conventional speakerphone 101 without a handset. In recent years, speakerphones 101 without handsets have become common, operating only in hands-free mode.